15 Magnetism 2020 J&N

The table shows the forces that exist between magnetic poles. Which row is correct?

A permanent magnet is to be made.

Which row gives the correct material to use and the correct reason for choosing this material?

Four nails A, B, C and D are tested to find which makes the strongest permanent magnet.

One of the nails is placed against a bar magnet and the number of paper clips which the nail can support is recorded.

The bar magnet is then removed and the number of paper clips remaining attached to the nail is recorded. Each nail is tested individually.

Which nail becomes the strongest permanent magnet as number of paper clips attached to the nail when bar magnet present and bar magnet removed are as followed?

• 2, 0

• 2, 1

• 4, 3

• 5, 2

The diagrams show two bar magnets which are attracting each other.

Which diagram shows the magnetic field pattern between the poles?

The diagram shows a magnet with some plotting compasses. The compasses show the direction of the magnetic field of the magnet. Which plotting compass has the needle pointing in the wrong direction?

The circuit shows one method of magnetising a steel bar.

How can the circuit be altered so that it can be used to demagnetise the magnetised steel bar?

• remove the steel bar from the coil whilst the current is switched on

• replace the d.c. supply with an a.c. supply and gradually reduce the supply voltage to zero

• reverse the polarity of the d.c. supply

• reverse the polarity of the d.c. supply and gradually reduce the supply voltage to zero

A student wants to demagnetise a steel bar. He uses the apparatus shown. He switches on the circuit for a few seconds and then switches off. He finds that the steel bar is still magnetised.

What should he do to improve his method?

• change the supply from an alternating to a direct voltage

• use a lower alternating voltage

• remove the steel bar from the coil whilst the circuit is switched on

• use a coil that has fewer turns on it

Two soft-iron pins are suspended from the S pole of a bar magnet.

Which diagram shows how the pins are deflected?

A student uses three small plotting compasses to investigate the magnetic field around a bar magnet.

Which diagram shows the directions in which the compass needles point?

A student sets up four experiments using bar magnets and other metal objects.

The N and S poles of the bar magnets are labelled N and S. Which pairs attract each other?

• 1 and 2

• 1 and 3

• 2 and 4

• 3 and 4